JPS6242554A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a capacitance section having sufficient capacitance and a transistor Tr having stable characteristics by directly applying a nitride film on a substrate in the capacitance section and shaping an SiO2 film on the substrate in a transistor forming section. CONSTITUTION:A field oxide film 12 and an SiO2 film 20 are shaped to a p-type Si substrate 11. A resist pattern 21 coating a transistor forming section is formed, and an n<+> type layer is shaped through ion implantation. When the film 20 is removed and the surface of the film 12 is removed partially, the surface of the substrate is exposed in a capacitance section, and the surface of the film 12 changed into an n<+> type is gotten rid of, thus generating no inversion. The film 20 is left under the pattern 21, a Tr forming section. When the pattern 21 is removed and a nitride film 22 is grown on the whole surface, the film 22 is formed to a section just above the substrate 11 in a capacitance forming section, the film 20 on the substrate 11 in the Tr forming section and the film 22 on the film 20, thus shaping the capacitance section having excellent characteristics and a transistor.

Description

[Detailed Description of the Invention] [Overview] Dynamic random access memory (dRA
In step M), after selectively forming an oxide film in the transistor forming area, a capacitor forming film is formed by depositing a silicon nitride film (hereinafter simply referred to as a nitride film).

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of forming a dRAM with excellent dielectric strength.

[Conventional technology]

FIG. 2(a) is a plan view and a cross-sectional view taken along line B-B in the same figure (d shown in bl) RAM is a known device, and in the figure, 11 is a p-type semiconductor (silicon). A substrate, 12 a field oxide film of silicon dioxide (5 iOz), 13 an n+ type region 14 a first layer polycrystalline silicon (polysilicon) film, 15 a second layer polysilicon film,
16 is an insulating film, 17 is an aluminum (1) wiring,
AJ wiring 17 is a bit line (data line)/2nd N
The polysilicon film is a word line (address line) and constitutes one memory cell in the illustrated device. FIG. 5C is an equivalent circuit diagram of the d RAM shown in FIG. In addition, in the same figure,
19 is a transistor forming section.

[Problem that the invention seeks to solve]

The capacitor section described above requires insulation resistance. Insulating films are generally made using the following three methods, and their insulation resistance is shown in the right column.

Type Insulating nitride film/5i02 Good 5i02
Defective 5i02/Nitride film/Si
In the third structure described above, a nitride film is deposited on 5i02 by chemical vapor deposition (CVD), and the surface of the nitride film is made into 5iOz by thermal oxidation. According to the requirements, the 5i02 film and the nitride film are each made to a thickness of 50 nm by controlling the growth, and the SiO2 film on the nitride film is
The thickness of the membrane shall be 10 people. The dielectric constant (ε) of 5i02 is 3.9, and the ε of the nitride film is 7, so converting the above three-layer structure to 5i02 corresponds to a film thickness of 75 people.

However, since it is advantageous for the insulating film to be thinner, the nitride film/
5i02 is more advantageous.

However, in the transistor formation area, it is necessary to apply SiO2 instead of immediately applying a nitride film to the substrate. The reason for this is that when SiO2 is placed on top of the nitride film, the film traps electrons and holes, the threshold voltage (V7/p) shifts, and the transistor characteristics change due to the interface state. becomes unstable, and the insulating film of the transistor must be 5iOz, and a nitride film is deposited on the silicon substrate, the nitride film is thermally oxidized, and then removed before a new 5i02 film is applied. If formed, the pressure resistance is poor,
By growing a 5i02 film and a nitride film on a silicon substrate, etching the nitride film and 5i02 in this order, and then performing thermal oxidation, a 5i02 film with good dielectric strength can be obtained in the transistor formation area.

Next, an equivalent circuit diagram of the capacitance section of the dRAM is shown in FIG. 3, where Cox is the capacitance of the insulating film and Cdep is the capacitance of the depletion layer formed in the silicon substrate.

However, when the concentration of the n+ layer is low, the equivalent circuit diagram of the capacitive part is shown in Figure 4, where there is an interfacial depletion layer Cn between the n+ layer and the 5i02 film, and Cn, which is equivalently smaller than Cox, appears on the surface. Therefore, sufficient capacity cannot be obtained. Therefore,
When enough impurities are implanted to increase the concentration of the n+ layer, the surface of the field oxide 11*12 becomes n+ type, and when it is reversed, the field oxide Ill! 12
There is a problem in that a current path is formed under the .

The present invention was created in view of these points, and an object of the present invention is to provide a method for manufacturing a dRAM having excellent dielectric strength and sufficient capacity.

[Means for solving problems]

FIG. 1 is a sectional view of an embodiment of the present invention.

In FIG. 1, when forming a dRAM on a semiconductor substrate, a nitride film is directly deposited on the substrate 11 in the capacitor part 18, and a SiO2 film is formed on the substrate in the transistor formation part, and then a SiO2 film is deposited on the substrate. A nitride film is deposited on the surface.

[Effect]

In the dRAM made by the above method, the nitride film is directly deposited on the substrate in the capacitor part, so a sufficient capacitance can be obtained using a thin nitride film, and in the transistor forming part,
Since a 5i02 film is formed on the substrate and a nitride film is deposited on it, a transistor with high dielectric strength and stable characteristics is formed.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG.
0 using conventional techniques.

Next, as shown in FIG. 1, a resist pattern 21 is formed to cover the transistor forming portion 19, and boron ions (B+) and arsenic ions (As'') are sequentially implanted to form an n+ type layer 13. In order to make the n+ type layer 13 sufficiently high in concentration, the As+ dose is lXl0''
5/Value should be 2 or more.

Next, as shown in FIG.
In step 8, the substrate surface is exposed, and the surface of the field oxide film, which has become n+ type due to the As+ ion implantation, is removed, and the above-described inversion no longer occurs. The 5i02 film 20 remains under the resist pattern, that is, in the transistor forming portion 19.

Next, as shown in the same figure (dl), resist pattern 2
1 is removed and a nitride film 22 is grown on the entire surface, a nitride film 22 of 5iOz Dm! is formed immediately on the substrate in the capacitor formation part 18, and a nitride film 22 of 5iOz Dm! is grown on the substrate in the transistor formation part 19. 20, a nitride film 22 is formed on the 5i02 film 20, and a capacitor portion and a transistor with excellent characteristics are formed.

Thereafter, the first polysilicon layer 14 and the second polysilicon layer 14 are formed using normal techniques.
A layer polysilicon layer 15 is formed, an insulating film 16 is deposited on the entire surface, and an insulating layer 1! ! After forming the electrode window on i16, A117
dRAM is completed.

〔Effect of the invention〕

As described above, according to the present invention, a nitride film is formed directly on the substrate in the capacitive part, and a 5i02 film and a nitride film are sequentially formed on the substrate in the transistor formation part.
A capacitor portion with sufficient capacity and a transistor with stable characteristics are formed using a thin insulating film, which has the effect of obtaining good characteristics of the dRAM.

[Brief explanation of drawings]

Figures 1 (a) to dl are cross-sectional views of the embodiments of the present invention, and Figure 2 (al is d RAM plan view, t'b) is the same figure (a).
A cross-sectional view taken along line B-B of , (C) is d l? of ta+. A
Fig. 3 is an equivalent circuit diagram of the capacitive part of d RAM in Fig. 2, and Fig. 4 is an equivalent circuit diagram of the capacitive part of d IIAH in Fig. 2 when the concentration of the n+ type layer is low. It is. 1 and 2, 11 is a silicon substrate, 12 is a field oxide film, 13 is an n+ type layer, 14 is a first layer polysilicon film, 15 is a second layer polysilicon film, and 16 is an insulating film. , 17 is the i-wiring, 18 is the capacitance section, 19 is the transistor formation section, 20 is the SiO2 film, Agent: Patent Attorney Sada Igeta - d-RAM'G, Kawao■ Figure 2

Claims (1)

[Claims] Field oxide film (1) on semiconductor substrate (11) of one conductivity type
2) and a step of forming an oxide film (20) on the element formation region, covering the transistor formation part (19) of the substrate (11) with a resist pattern (21), and forming the capacitance part (18) with a conductivity type opposite to that of the substrate. Diffusion of impurities into a layer of conductivity type opposite to that of the substrate (1
3) forming the oxide film (20) of the capacitive part (18) and the field oxide film (
Step 12) of removing the impurities diffused into the field oxide film by etching the surface of the resist pattern (21), depositing a silicon nitride film on the entire surface, and then removing the impurities diffused into the field oxide film. A method for manufacturing a semiconductor device characterized by forming a capacitor and a transistor in a transistor forming portion (19).